It all depends on whether or not you like how a blend changes as it ages. People like to say that blends get better with aging. I disagree with that statement. Blends change as they age. Whether that change is an improvement is dependent on the taste of the smoker.
Pease has written on this and I often suggest to smokers that they refer to his
faq - Pease on aging. The biggest changes happen in the first 5 years. After that the changes are more gradual.
If you like the sharper flavors of younger tobaccos, if you like being able to pick out the various components in a blend, then aging may not be for you, at least long term aging. One of the aspects of the changes that happen with long term aging is that the components marry over time, creating a unified flavor profile with less variation from sip to sip.
I like the effect that aging has on some blends, like Escudo, which I also like fresh, but find it less of a benefit with others, like Stonehaven. I prefer Haddo's with a decade of aging on it because the bit of harshness that I experience with it when fresh is smoothed out. And I've smoked certain vintages of Christmas Cheer fresh and with many years of aging and haven't found that much of an "improvement" with the added years, or none whatsoever, just a change in the flavor.
Eventually, all blends go south. The really ancient tobaccos I've sampled over the years, 50 to 100 years old, have largely been sludge, zombie poop, wraiths, or mummy dust. Once in a while I get to experience something really remarkable, but it's very hit or miss.
And the reality is that a great number of blends are going to disappear in the next few years, so if you want to smoke them, you need to buy them when available. If aging is not for you, you can jar those blends and use a pump to remove the remaining oxygen so that they are vacuum sealed, and that will retard, though not completely stop, the aging process. The flat tins, at least the new ones, are slowly leaking from the get go, aren't going to hold up over the long term anyway, so why not jar them?